The invention relates to a device for releasing a mechanical energy storage means, especially a prestressed spring, in a release situation. Such a device is, for example, required in the field of tensioning devices for safety belts, especially in motor vehicles, in which a prestressed spring is released by a sensor so that the energy stored within the spring may be transmitted into the execution of a tensioning movement of the safety belt.
With such devices in general the following problem is encountered: When employing movable securing members, a considerable friction between the mechanical energy storage means that is secured, respectively, that is to be released, and the securing member, respectively, the components employed for the releasing function must be overcome because the securing member, respectively, the components employed for the releasing function must bear the full force of the energy storage means. A further problem is that the release of the securing member, respectively, the energy storage means must occur within a very short activation time in order to prevent an endangerment of the buckled-in passengers during an accident.
For securing the energy storage means in its locked position, it is also known to provide a locking lever which is resting in a prestressed manner on a supporting means in the locked position, whereby the supporting means is deflectable in the release situation by an acceleration-sensitive release member.
A device of the aforementioned kind employed in safety belts in motor vehicles is described in European patent application 0 305 765. In this known device, the deflectable support for supporting the locking lever which maintains the energy storage means in its locked position is in the form of a vertically arranged sensor lever having, at a free end extending in an upward direction, an inertia member and being supported in its vertical initial position by spring means. The vertically extending sensor lever is coupled via an additional lever system to the locking lever for pivoting it out of its locking position.
The known device has the disadvantage that the arrangement of the sensor lever with its inertia member as the acceleration-sensitive release member for the locking lever and the required mechanical coupling with the locking lever results in a complicated constructive embodiment with plurality of interacting and cooperating components. It is therefore difficult to adjust the threshold for the movement of the locking lever into the release position for the energy storage means and to maintain this threshold with the necessary exactness during operation.
It is known from European patent application 0 300 469 to provide an elbow lever between a locking lever and an inertia sensor, whereby however the inertia sensor is of a complicated construction.
It is therefore an object of the invention to provide a device for releasing a mechanical energy storage means with which a secure and fast release of the mechanical energy storage means is ensured. It is another object of the present invention to simplify design of the acceleration-sensitive release member for the locking lever and to improve the functional reliability of the device.